The present invention relates generally to foam-in-place or foam-in-bag cushions used as protective cushioning materials for product packaging. The invention relates more particularly to a system and method for molding such foam cushions into desired shapes.
Foam-in-place packaging is a highly useful technique for on-demand protection of packaged objects. In its most basic form, foam-in-place packaging comprises injecting a foam-forming composition from a dispenser into a container that holds an object to be cushioned. Typically, the object is wrapped in plastic to keep it from direct contact with the rising (expanding) foam. As the foam rises, it expands into the void space between the object and its container (e.g., a corrugated board box), thus forming a custom cushion for the object.
A common foam-forming composition is formed by mixing an isocyanate compound with a hydroxyl-containing material, such as a polyol (i.e., a compound that contains multiple hydroxyl groups), typically in the presence of water and a catalyst. The isocyanate and polyol precursors react to form polyurethane. At the same time, the water reacts with the isocyanate compound to produce carbon dioxide. The carbon dioxide causes the polyurethane to expand into a foamed cellular structure, i.e., a polyurethane foam, which serves to protect the packaged object.
In other types of foam-in-place packaging, an automated apparatus produces foam-in-bag cushions by making bags from flexible plastic film and dispensing a foam-forming composition into the bags as they are being formed. As the composition expands into a foam within a bag, the bag is sealed shut and typically is then dropped into a container holding the object to be cushioned. The rising foam again tends to expand into the available space, but does so inside the bag. Because the bags are formed of flexible plastic, they form individual custom foam cushions around the packaged objects. Exemplary types of such packaging apparatus are assigned to the assignee of the present application, and are illustrated, for example, in U.S. Pat. Nos. 4,800,708, 4,854,109, 5,027,583, 5,376,219, and 6,003,288, the entire disclosures of each of which are incorporated herein by reference.
In some applications, it is desirable for the foam cushions to have a certain predetermined shape. For example, it may be desirable for the cushions to be made in advance of a packaged object being placed into a carton. In such instances, it is desirable for the cushions to fit properly about the object and/or against the inner walls of the carton, and therefore it is necessary to mold the cushions to have the correct shape. Accordingly, a molding system and method are needed.
Current systems for molding foam cushions generally comprise a mold defining a mold cavity that is a negative impression of the desired shape of the cushions to be produced. The mold has a door that is closed after the expanding foam cushion is placed inside the mold cavity. The cushion is allowed to substantially fully expand within the mold cavity, and the door is then opened and the molded foam cushion is removed. In some molding systems, some or all of these actions are performed manually by a worker. In other cases, fully automatic molding systems have been developed employing a foam-in-bag cushion-making apparatus and a plurality of molds that are sequentially supplied with expanding cushions from the apparatus, wherein the cushions are automatically placed into the molds and then are automatically removed from the molds using mechanical devices such as rods that push the molded cushions out of the molds. The mechanical devices can cause distortion of the molded cushions.
It is desirable to automate the molding process to as great an extent as possible and to improve upon existing automated systems.
Additionally, in current cushion-molding processes, it is often difficult to ensure that the cushion settles fully into the mold cavity when placed therein. If the cushion does not properly settle into the cavity, the expanding cushion may not completely fill out all regions of the cavity, and the resulting molded cushion may have defects in shape that can render the cushion unusable for its intended purpose.
Thus, it is desirable for an automated system and method to ensure proper settling of the expanding cushion into the mold cavity.